Pulper



July 15, 1969 N. F. HOCH 3,455,516

PULPER Filed Jan. 11, 1957 5 Sheets-Sheet l j- INVENTOR.

11/51 324 Ffiacfz N. F. HOCH July 15, 1969 PULPER 5 Sheets-Sheet 2 Filed Jan. 11, 1967 1 N VENTOR.

3,455,516 PULPER Norman F. Hoch, Pittsfield, Mass., assignor to Beloit Corporation, Beloit. Wis., a corporation of Wisconsin Filed Jan. 11, 1967, Ser. No. 608,584 Int. Cl. B02c 7/08, 13/14 US. Cl. 24146.17 Claims ABSTRACT OF THE DISCLOSURE Background of the invention The general field to which the present invention pertains is the field of papermaking, and more particularly to the field of reclamation of broke or off-grade paper from a paper machine.

For example, occasionally during the operation of a paperrnaking machine the web, for one reason or another will become damaged and will break somewhere within the machine. While the damaged web portion of the web is cut and the freshly cut end fed through the remainder of the papermaking machine to resume normal operations just as soon as possible, the length of web that is cut off may be sufficient to constitute a significant loss. This is especially true in a high speed machine operating, for example, in the range of 2,000 to 3,000 feet per minute. A break which lasts only a minute or so can result in a tremendous loss of the product.

The damaged and cut web is called broke. In order to salvage broke it is generally conveyed to a pulper where it is mixed with water in a tank and thoroughly churned by means of one or more pulping rotor assemblies within the tank to again form pulp or stock, and then again circulated to the papermaking machine to form web.

As is true in most machinery, the efiiciency of a pulper is of paramount importance. This is particularly so in the case of a continuously operated pulper, as contrasted with a pulper operated only periodically. A significant indicator of efiicieny is the rate of submergence, that is, the rate at which the broke or off-grade paper loaded from the top of the pulper is drawn down under the slurry already being mixed in the pulper.

Many efforts have been made in the past to increase the rate of submergence of pulpers without sacrificing size and cost of operation. However, insofar as I am aware none of the prior investigators have discovered the relationships described herein which relate to the shape of the tank and the direction of rotation of the rotor assemblies, and which have a direct bearing on the rate of submergence.

Summary of the invention Briefly, a pulper constructed according to the principles of this invention comprises an oblong tank enclosed at the bottom and having an upstanding side wall with arcuate ends. Two or more pulping rotors are mounted within the tank for rotation on spaced vertical axes. The rotors are in substantial coplanar relationship with and nite rates Patent 0 Patented July 15, 1969 completely surrounded by horizontally extending portions of the bottom wall of the tank. Means are pro vided for driving the rotors in the same direction of rotation.

The tank is symmetrical about transverse and longitudinal centerlines and the axes of rotation of the rotors are located along the longitudinal centerline of the tank. If an even number of rotors are used they are arranged allochirally in equal numbers on both sides of the transverse centerline of the tank, whereas if an odd number of rotors are used the middle rotor is situated at the center of the tank.

In one respect the present invention involves the disdiscovery of certain relationships between the center-tocenter distances of the rotors and the length and width of the tank of a multi-rotor pulper which provide improved rates of submergence and efficiency. For example, I have determined that a distance between the axes of the rotors of a two or three rotor pulper of between 1.4 and 2 times the diameters of the rotors provides exceptional operating characteristics. Certain other relationships between the diameters of the rotors and the length and width and length/width ratios of the tank all of which are set forth in detail hereinafter, also afford improved operation.

The present invention further involves the discovery of improved submergence factors as a result of surrounding the rotors with flat coplanar portions of the bottom wall of the tank. In this arrangement only a single vortex is produced in the pulp rather than, for example, two or three vortices produced respectively in presently known two or three rotor pulpers. The single vortex provided by the present invention further improves submergence factors.

It is, therefore, an object of the present invention to provide an improved pulper for continuously pulping wastepaper products.

A more specific object of the present invention is to improve the submergence factor and efficiency of pulpers.

Another object of the present invention is to improve the operation of a multi-rotor pulper by producing only a single vortex in the pulp as contrasted with multiple vortices.

A further object of the invention is to provide a pulper having certain relationships between the diameters of the rotors and the length, width and length/width ratio of the pulper tank to improve the operating characteristics of the pulper.

Another object of the invention is to improve the submergence factor of a pulper by surrounding the rotors with flat coplanar portions of the bottom wall of the pulper tank.

Many other features, advantages and additional objects of the present invention will become manifest to those versed in the art upon making reference to the detailed description which follows and the accompanying sheets of drawings, in which preferred structural embodiments incorporating the principles of the present invention are shown by Way of illustrative example only.

Brief description of the drawings FIGURE 1 is a top plan view of an improved pulper constructed in accordance with the principles of the present invention.

FIGURE 2 is a vertical cross-sectional view of the pulper shown in FIGURE 1 taken along lines IIII of FIGURE 1;

FIGURE 3 is another vertical cross-sectional view of the pulper shown in FIGURE 1 taken along lines IIIIII;

FIGURE 4 is a top plan view of another embodiment of a pulper constructed in accordance with the present invention; and

FIGURE 5 is an enlarged section of a rotor of the present invention with portions thereof shown in elevation.

Description of the preferred embodiments FIGURES 1-3 illustrate one embodiment of a pulper constructed according to the present invention and FIG- URE 4 illustrated another embodiment. The embodiment of FIGURES 1-3 has three rotor assemblies, whereas the pulper shown in FIGURE 4 has only two such assemblies.

The pulper shown in FIGURES 1-3 is indicated generally at reference numeral and comprises a tank 11 which is open at a top end 12 and enclosed at the bottom by means of a bottom wall 13. An upwardly extending side wall 14 encloses the sides of the tank 11 and comprises a pair of spaced parallel longitudinal walls 16 and 17 which extend in parallel relation to the longitudinal centerline of the tank 11 and a pair of spaced parallel end walls 18 and 19 extending transversely to the longitudinal centerline.

The interior of the tank, indicated generally at reference numeral 20, receives the deposits or charges of wastepaper product from the open top end of the tank 11. The wastepaper product may be dumped into the tank by any suitable means such as an overhead endless conveyor system. Water as well as other additives are added through the top end 12 of the tank although these ingredients may also be supplied through conduits or pipes extending through the walls of the pulper.

The interior 20 of the tank 11 is oblong and symmetrical about longitudinal and transverse centerlines of the tank. Three pulping rotor assemblies 21, 22 and 23 are situated within the tank and spin on vertically rotatable shafts 21a-23a arranged along the longitudinal centerline of the tank 11.

Each of rotor assemblies 21-23 comprises an impeller 24. The impellers 24 are driven independently of each other by means of three separate motor drives 21b- 23b situated below the bottom wall 13 of the tank 11. Each of the motor drives 21b-23b comprises a constant speed electric motor, although the principles of this invention are susceptible to other types of drive mechanisms.

The rotor assemblies 21-23 are similar in design and as shown in the enlarged sectional view of rotor 21 shown in FIGURE 5 each comprises a series of radially extending impeller blades 26 mounted on the impeller 24. An extraction grate 27 bottoms on a peripheral flange 28 of of the assembly 21 and is apertured as at 29 to enable the mixed pulp or slurry to flow through the grate 27 and into an extraction chamber 30, from which it flows through an outlet drain 31a back to the papermaking machine.

As previously noted, a significant indicator of the efficiency of a pulper is generally designated as the submergence factor or rate of submergence. This designation refers to the speed with which the rotor assemblies 21-23 submerge the wastepaper products from the top of the pulp in the tank down into the pulp. In other words, the greater the rate in which the wastepaper products are submerged and assimilated into the pulp the greater the efiiciency of the pulper.

Multiple rotor assemblies have been provided in known pulpers but in these arrangements each of the impellers generates its own vortex. Thus if a prior art pulper comprises three impellers, three spaced vortices are generated within the tank. The present invention involves among others the discoveries that the rate of submergence is increased in multiple impeller pulpers if only one vortex is generated within the tank, and that a single vortex can be generated with multiple impellers if certain design parameters are satisfied.

In accordance with the present invention all of the impellers are driven in a single direction of rotation. For example, in the plan view of FIGURE 11 all of the rotor assemblies 21-23 rotate in a clockwise or in counterclockwise direction, depending upon the design characteristics of the particular impellers involved. Regardless of whether the impeller design makes clockwise or counterclockwise rotation more desirable, however, all of the impellers are rotated in the same direction. The arrows indicated in FIGURE 1 represent a clockwise direction of rotation of the impellers 24 of the illustrated embodiment.

Another feature of this invention which confers more rapid submergence and assimilation of the wastepaper product pertains to the design of the interior 20 of the tank 11. The interior 20 is oblong in shape and is bounded on the sides by a pair of longitudinally extending interior side walls 32 and 33 and on the ends by a pair of arcuately shaped interior end walls 34 and 36.

An interior bottom wall 37 surrounds the rotor assemblies 21-23 and extends substantially horizontally in coplanar relation with the radial plane of the impellers 24, that is, substantially in alignment with the extraction grate 27 and the peripheral flange 28 of each of the rotor assemblies 21-23. The interior bottom wall 37 is joined to the interior side walls 32 and 33 and end walls 34 and 36 by a pair of identically shaped oppositely facing inclined walls 38 and 39.

In order to facilitate overhead loading of the tank 11 with the wastepaper product a downwardly inclined wall 40 is provided at each of the four corners of the tank and an inclined ramp 41 extends along a center portion of the interior side wall 33 above which the conveyor carrying the wastepaper product to the tank 11 may be located.

The axis of rotation of the middle rotor assembly 22 is situated at the intersection of the longitudinal and transverse centerlines of the tank 11 and the axes of rotation of assemblies 21 and 23 are spaced along the longitudinal centerline of the tank 11 equal distances from the axis of rotation of rotor assembly 22. The distances that the rotors are spaced from each other as well as the length and width of the interior 20 of the tank 11 relative to the diameters of the impellers or rotors 24, assemblies 21-23 are important considerations in this invention.

The chart shown in FIGURE 6 illustrates in tabular form the results of tests which I have conducted to determine the quality of the circulation and submergence of wastepaper product when deposited in pulpers constructed in accordance with this invention as a function of rotor spacing and as a function of the length, the widths and the length-width ratios of the tanks. The tests were conducted on a three rotor pulper as shown in FIGURES 1-3 as well as a two ortor pulper as shown in FIGURE 4.

With respect to the spacing between the impellers or rotors 24 (rotor centers in the chart of FIGURE 6) the tests indicate that the rate of circulation and submergence of wastepaper product ranges from excellent to good when the distances between the rotors of a two or three rotor pulper are between 1.4 and 2.0 times the diameters of the rotors. The diameters of the rotors of each of the pulpers were substantially equal to each other.

The tests also indicate results ranging from good to excellent regarding circulation and submergence when the width of the tank of a two or three rotor pulper is between two and four times the diameters of the rotors. The results also range between good and excellent where the length of the tank of a two or three rotor pulper ranges between 4.8 and 7.0 times the diameters of the rotors. The terms tank width and tank length as used in FIGURE 6 refer, of course, to the width and length of the interior of the tank, since it will be appreciated that the external or outside dimensions of the pulper tank are immaterial.

The results further indicate that results ranging from good to excellent are obtained when the length/width ratio of a two or three rotor pulper is between 4:3 and 3: 1.

In conducting tests within all of the preferred ranges noted hereinabove, only one vortex was generated in the slurry, as contrasted with multiple vortices generated in the multi-rotor pulpers of the prior art. The generation of only a single vortex doubtless greatly increases the rate of submergence.

With the exception of the numbers and location of rotor assemblies, the two-rotor pulper illustrated in FIG- URE 4 is similar in all material respects to the pulper shown in FIGURES 1-3.

In the FIGURE 4 embodiment, wherein structures similar to those shown in FIGURES 13 are designated by means of the same reference numerals raised by 100, the two rotor assemblies are indicated at 121 and 122. Since there are only two impellers 124 they are spaced equidistantly from the center of the tank, the point at which the longitudinal and transverse centerlines intersect. In other words, according to the principles of this invention in pulpers comprising an odd number of impellers, the axis of rotation of the middle impeller is at the center of the tank and the remaining impellers are evenly divided and spaced at equal distances on the opposite sides of the tank center. In pulpers comprising an even number of impellers, however, the impellers are evenly divided on opposite sides of the tank center and none of the impellers is located at the center of the tank.

Although minor modifications might be suggested by those versed in the art, it should be understood that I wish to embody within the scope of the patent warranted here on all such modifications as reasonably come within the scope of my contribution to the art.

I claim as my invention:

1. A pulper for mixing paper sheet material to form a pulp comprising,

an elongated tank having arcuate ends and a planar bottom portion,

at least two pulping rotors arranged along the longitudinal eenterline of the tank and rotatable about a vertical axis, and means for rotating the rotors to generate a single vortex for submerging sheet material placed in said tank,

said planar bottom portion extending in a substantially horizontal plane radially outwardly from and continuously around all of said rotors and in substantially co-planar relationship therewith.

2. The pulper as defined in claim 1 wherein said tank is oblong in shape and has a length to width ratio of between 4:3 and 3:1.

3. The pulper as defined in claim 1 wherein said rotors are further arranged allochirally relative to the center of the tank.

4. The pulper as defined in claim 1 wherein said rotors are spaced apart a distance less than twice the diameters of the rotors.

5. A pulper for mixing paper sheet material to form a pulp comprising,

an oblong tank symmetrical about a transverse centerline and having a horizontal bottom wall,

an upstanding continuous side wall surrounding the tank and an inclined wall interconnecting the bottom and side Walls,

a plurality of pulping rotors mounted within said tank having vertical axes of rotation disposed along the horizontal centerline of said tank,

a plurality of peripheral flanges surrounding said pulping rotors, said rotors and said peripheral flanges being substantially co-planar with and within the hori zontal confines of said bottom wall whereby the bottom wall extends radially outwardly beyond the tips of said rotors and said peripheral flanges, and

means for rotating said rotors about the vertical axes thereof.

6. The pulper as defined in claim 5 wherein said tank has a length to width ratio of between 4:3 and 3:1.

7. The pulper as defined in claim 5 wherein the axes of rotation of said rotors are spaced from each other equal distances of between 1.4 and 2 times the diameters of said rotors.

8. The pulper as defined in claim 5 wherein said rotating means drives all of said rotors in the same direction of rotation.

9. The pulper as defined in claim 5 wherein the length of said tank is between 3.8 to 8.7 times the diameters of said rotors.

10. The pulper as defined in claim 5 wherein the width of said tank is between 2 and 4 times the diameters of said rotors.

References Cited UNITED STATES PATENTS 2,434,449 1/ 1948 Wells 241-4617 2,583,997 1/1952 Chester 241-46.11 2,789,772 4/1957 Williamson 24l46.02 2,860,550 1-1/1958 Stark 24l46.02 X 3,009,656 11/1961 Martindale 24146.17 3,342,425 9/ 1967 Morton 241-46.11

ROBERT C. RIORDON, Primary Examiner D. G. KELLY, Assistant Examiner 

